The present invention relates to an automatic transmission having an oil filter that is attached to a transmission casing.
In a related art, an automatic transmission through which oil discharged from an oil pump through a control valve unit is circulated in a transmission casing as lubricating oil after passing through an oil cooler and an oil filter has been known. For example, such an automatic transmission is disclosed in Japanese Patent Provisional Publication No. 2003-106415 (hereinafter is referred to as “JP2003-106415”).
In this related art automatic transmission, an opening end surface of a filter case having therein the oil filter is contiguous with or touches the transmission casing, and a circumferential edge portion of this opening end surface is fixed with a plurality of screws. Further, a seal member is provided on a contact surface between the transmission casing and the filter case, and thereby preventing oil leakage.